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The charged pion production reactions d(gamma,pi⁺n), d(gamma,pi^-p), HD(gamma,pi⁺n)X were studied using linearly polarized gamma-rays with energies in the range from 260 MeV to 370 MeV at the Laser Electron Gamma Source (LEGS). A solid HD target was used in this experiment for the first time. The beam asymmetry data for the d(gamma,pi^-p) reaction significantly add to the previously available data. This gives new input to multipole analysis of pion production. A slight deviation from the beam asymmetry predicted for the free neutron is observed. The cross sections in the d(gamma,pi^-p) channel agree with previous measurements. / Ph. D.

Remote detection and tracking of wingtip generated wake vortices is important for hazard avoidance especially near airports. Aircraft that fly through these hazardous vortices experience sudden induced roll. Experiments have demonstrated that there is sufficient radar cross section for remote detection at frequencies ranging from VHF to C band (100 MHz to 5 GHz). The mechanism that yields this radar cross section is Bragg scattering from the index of refraction variations due to the atmospheric water vapor and potential temperature fields being mixed by the wake vortex system. Refractive index variations of the size that correspond to half the operating radar wavelength produce the observed radar return. Previous analysis has postulated turbulence within the wake vortex to be the generator of the index of refraction variations. In this work, a new mechanism is identified that does not assume turbulence within the wake vortex system. This "laminar flow mechanism" causes refractive index structuring that stretches into successively smaller spirals over time as the wake vortex system swirls and descends through the stratified atmosphere. The results are quantitatively consistent with experimental data. Results indicate that this new mechanism has a sharply peaked doppler spectrum which is encouraging for coherent detection by doppler radar. / Ph. D.

The project began as a response to a proposal to construct a suburban style grocery store and surface parking lot in the middle of an existing residential neighborhood, including the substantial demolition and 'strip-mall' conversion of a historic theater located on the Washington, DC site. The Thesis evolved as an exploration of how do we reconcile our contemporary mercantile needs within the urban environment; specifically, how can one incorporate a suburban-scaled, 'big-box' retail structure in an existing, complex urban context. The proposal that follows offers an integrated, mixed-use and contextually sensitive solution, incorporating a full size grocery store (the most fundamental of our consumer needs) with multiple levels of parking below, new residential row-housing and commercial space above - retaining and restoring both the historic theater and the overall neighborhood fabric. / Master of Architecture

Currently, the design model for flexural rupture of an eccentrically loaded bracket plate is based on the material tensile rupture strength times the net elastic section modulus. Different bolt and plate sizes were tested to determine if this model is correct. It was found that the current model is conservative and that the material tensile rupture strength times the net plastic section modulus is a superior design model. Also, limited finite element modeling was performed to predict the elastic stiffness of such connections. The resulting data correlates well with test results, and confirms that most of the connection ductility comes from bolt plowing. These results can be used for splice plate connections in cantilever construction, as well. / Master of Science

The nation's Section 404 permitting program, of the Clean Water Act (CWA), represents one of the longest regulatory histories of designing and implementing credit trading programs to satisfy regulatory requirements. The role and the function of in-lieu fee (ILF) programs in supporting this regulatory structure have undergone a substantial change. For the first time in the history of the Sec. 404 program, 33 CFR Part 332 and 40 CFR Part 230, Subpart J (the "2008 mitigation rule" or "rule"), prioritizes the use of off-site mitigation over on-site-mitigation. Additionally, the rule prioritizes advanced, third-party mitigation; especially as achieved through mitigation banks; over any off-site compensatory mitigation provided by ILF programs (33 CFR 332.3(b)(1)). This new regulatory environment favors the use of commercial mitigation bank credits while acknowledging that the limited permittee demand of off-site mitigation credits, in particular areas, justifies the continuing need for ILF programs (Corps and EPA 2008, p.19606,19611). This research examines how regulatory officials use ILF programs under the 2008 mitigation rule, and, it determines the extent to which ILF programs are capable of fulfilling the role envisioned for them under the 2008 mitigation rule. Simulation results indicate that commercial mitigation banks cannot meet risk adjusted returns under limited credit demand conditions. ILF programs offer some additional financial capacity to fill the void in commercial bank coverage; but, this potential is limited in low demand conditions. Furthermore, empirical case studies of a Virginia and Georgia provide evidence that regulatory officials rely on ILF programs to provide off-site compensatory mitigation almost exclusively in the absence of private credit supply, as intended in the 2008 rule. Evidence in Georgia and Virginia also indicate that, in some situations, ILF programs face difficulties in providing mitigation under the constraints of limited demand and more stringent regulatory requirements. / Master of Science / National permitting programs require people that impact wetlands or streams to offset unavoidable, adverse impacts by improving wetlands or streams elsewhere, a process called compensatory mitigation. A new regulatory rule, approved in 2008 (33 CFR Part 332 and 40 CFR Part 230, Subpart J), prioritizes that mitigation is provided at larger projects off-site of the impact. Key policy questions of “who should provide the mitigation?” and “when the mitigation should be provided” were an important part of the debate during the rule’s development. Wetland and stream mitigation may be provided by commercial (for profit) businesses, called mitigation banks. Commercial banks make wetland/stream improvement projects before permitted (adverse) impacts occur in anticipation of selling wetland/stream “credits” (quantified levels of improvement). Off-site mitigation may also be provided by in-lieu fee (ILF) programs operated by the government or nonprofit organizations. ILF programs first accept funds from permittees and then construct mitigation projects once sufficient funds have been collected, thus creating a lag between adverse impact and compensatory mitigation. The 2008 regulatory rule favors the use of commercial mitigation bank credits over ILF credits, but allows regulatory officials, under certain circumstances, to use ILF credits when commercial bank credits of the appropriate type are unavailable. This research examines how regulatory officials use ILF programs, and it investigates the extent to which ILF programs are financially capable of providing off-site mitigation in situations where the appropriate commercial credits are unavailable. A financial simulation model is developed to examine the feasibility of mitigation projects under different costs and credit demand conditions. Results indicate that commercial mitigation banks cannot meet financial objectives under limited credit demand conditions. ILF programs offer some additional financial capacity to fill the void in commercial bank coverage, but ILF programs also face financial limitations under conditions with low demand for credits. Empirical case studies of Virginia and Georgia provide evidence that regulatory officials rely on ILF programs to provide off-site compensatory mitigation almost exclusively in the absence of a private credit supply, as intended in the 2008 rule. However, evidence in Virginia and Georgia also affirm that ILF programs face difficulties in providing mitigation in some situations of limited demand and stringent regulatory requirements.

Several aesthetic, health, and plumbing quality issues can arise during new construction or renovation of premise plumbing. There has been little research done on many of these concerns and therefore few guidelines or regulations are in place to protect the health of the consumer or the integrity of the plumbing infrastructure. This work examines common construction practices including: 1) effect of residual construction debris, 2) shock chlorination of new plumbing lines, and 3) lead leaching propensity of new brass ball valves. During installation of plumbing systems, residual chemicals and debris including copper brass particles and flux, can be left in plumbing lines following construction and installation. This debris is considered undesirable from health, aesthetic, and corrosion perspectives. Soldering flux is of particular concern due to its corrosive nature. Experiments were conducted to determine the effects of residual solder flux, PVC glue, and metallic debris and to quantify flushing velocities and durations to effectively remove them from a new plumbing system. A flushing velocity of 3 fps for 30 minutes is needed to remove water soluble flux, while petroleum based flux still persists after extensive flushing at 7 fps. Currently a practice known as shock chlorination, whereby super chlorinated water is used for disinfection, is used in water mains after installation or repair as specified in the ANSI/AWWA C651 Standard. This practice is now starting to be required by some building codes in premise plumbing for new construction. Water mains are typically made of concrete where as premise plumbing using copper or PVC piping. Copper pipe is susceptible to attack by high chlorine, and this reaction will also remove the chlorine residual. There is concern about potential damage to copper from free chlorine and that in some systems targeted residuals of chlorine might not be obtained. Experiments did not detect serious damage to copper pipe, but in some waters it was not possible to meet targeted residual levels of chlorine. The addition of orthophosphate corrosion inhibitor or adjustment of pH can sometimes reduce the chlorine decay rate. Extremely high and persistent lead leaching in a brand new building at the University of North Carolina (UNC) traced to leaded bronze ball valves, prompted an extensive forensic evaluation how existing standards (National Sanitation Foundation Section 8) could allow for installation of products that could create a human health hazard due to high lead. Diffusion of lead from within the device to water in the pipe, high velocity, microbial activity and other factors caused more leaching in practice than would be expected based on NSF testing and normalization factors applied to certify a valve as safe. Moreover, use of flux during soldering of joints, increased lead leaching by orders of magnitude relative to results of NSF testing without flux. / Master of Science

The ban on lead plumbing materials in the Safe Drinking Water Act (1986) and the EPA Lead and Copper Rule (1991) have successfully reduced lead contamination of potable water supplies. The success of these regulations gave rise to a belief that serious lead contamination was an important past problem that had been solved, and that additional fundamental research was therefore unnecessary. This work carefully re-examined the lead contamination issue from the perspective of 1) new regulations causing a shift from chlorine to chloramine disinfectant, 2) assumptions guiding sampling strategies, 3) existing performance standards for brass, and 4) galvanically driven corrosion of lead bearing plumbing materials. The results were instrumental in uncovering and understanding a serious problem with lead contamination in Washington, D.C. A critical reading of the literature indicates that chloramines can accelerate corrosion of lead bearing materials and increase lead contamination of water. When a new sampling protocol was conceived and used in Washington homes to assess the nature of the problem, hazardous levels of lead were found to be present in some drinking water samples. Contrary to the conventional wisdom, lead was not always highest in first draw samples, but often increased with flushing. This has several important implications for monitoring and public health. For instance, well-intentioned public education materials were causing consumers to drink water containing very high levels of lead in some circumstances. Laboratory and field-testing proved that chloramines were causing serious lead corrosion problems. That testing also discovered that, unbeknownst to scientists and utilities, free chlorine itself can act as a corrosion inhibitor, reducing lead solubility and contamination of water. The net result is that changing disinfectant from free chlorine to chloramine can sometimes trigger serious lead contamination of water. While the worst problems with lead in Washington, D.C. came from the lead services, significant levels of lead were occasionally sampled from homes with solders or brass as the lead source. This prompted re-evaluation of the ANSI/NSF 61, Section 8 standard, which is relied on to protect public health from in-line brass plumbing devices that might leach excessive lead to potable water. In-depth study of the standard revealed serious flaws arising from use of a phosphate buffer in the test waters and a failure to control carbonate dissolution from the atmosphere. Due to these deficiencies, small devices made of pure lead could actually pass the performance test. The public therefore has no assurance that devices passing NSF Section 8 testing are safe and reforms to the standard are obviously needed. Other problems arise from connecting copper pipe to lead bearing plumbing in practice. The copper is cathodic and dramatically accelerates corrosion of the lead anode via a galvanic current. Corrosion and hydrolysis of released Pb²⁺ can lower pH near the surface of the lead and increase its solubility. A similar galvanic effect can arise from cupric ions present in the water via deposition corrosion mechanism. In cases where part of a lead service line is replaced by copper pipe, the galvanic corrosion effect can create a serious long-term problem with lead contamination. Such partial lead service line replacements are occurring in many US cities and the practice should be stopped. Lead contamination of potable water is not only a problem of the past but also of the present. While additional research is necessary before regulators, utilities and homeowners can anticipate and mitigate such problems with confidence, this work provides sound fundamental basis for future progress. / Master of Science

The series of experimental studies to be described has been carried out in order to determine the feasibility of using corner reflectors as laboratory standards for model cross-section measurements.

Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Background Caesarean section deliveries are the most common procedures performed by obstetricians in Zimbabwe. Surgical site infections (SSI) following caesarean section delivery result in increased hospital stay, treatment, cost, hospital readmission rates and related maternal morbidity and mortality. There is no national surveillance system for SSIs in Zimbabwe, however, information is available on number of cases of post-operative wound infection after caesarean section, but the denominator and definition used is not consistent. The objective of this study were develop and strengthen the surveillance system in Zimbabwe, to establish a clinical-based system in a setting with limited microbiological access, to measure post-operative SSI after caesarean section and to describe the associated risk factors and to determine whether feedback of SSI data has any effect on the surgical site infection incidence rate. Methodology This was a before and after study with two rolling cohort periods conducted at two Central hospitals in Harare, Zimbabwe. An Infection Prevention and Control (IPC) intervention was conducted in-between. During the pre-intervention period, baseline demographic and clinical data were collected using a structured questionnaire, and during the post-intervention period the impact of the interventions was measured. Convenience sampling was employed. Results A total of 290 women consented to participate in the study in the pre intervention period, 86.9% (n= 252) completed the 30-days post-operative follow-up and the incidence rate of SSI was 29.0% (n=73, 95% CI:23.4-35.0) Interventions developed included: training in Infection Prevention and Control for health workers; implementation of a protocol for cleaning surgical instruments; dissemination of information on post-operative wound management for the women. After implementation of the intervention, 314 women were recruited for the post-intervention, 92.3%(n= 290) completed the 30-day follow-up and there was a significant (p<0.001) reduction in the incidence rate of SSIs to 12.1 % (n=35, 95% CI: 8.3 -15.8) during this period. Development of SSI after caesarean section was found to be significantly associated with emergency surgery (p<0.001), surgical wound class IV (p=0.001) and shaving at home (p<0.001) at both pre- intervention and post-intervention periods. Stellenbosch University https://scholar.sun.ac.za iii Conclusion This study shows that caesarean section can be performed with low incidence of SSI if appropriate interventions such as training in IPC, adequate cleaning of equipment and education in wound-care for the mother are adhered to. It also demonstrated a simple surveillance data collection tool can be used on a wide scale in resource limited countries to assist policy makers with monitoring and evaluation of SSI rates as well as assessment of risk factors. / AFRIKAANSE OPSOMMING: Agtergrond Keisersnitte is die mees algemene prosedure wat uitgevoer word deur obstetriese dokters in Zimbabwe. Chirurgiese wond infeksies wat op keisersnitte volg lei tot verlengde hospitaal verblyf, behandeling, koste, heropname koerse en verwante moederlike morbiditeit en mortaliteit. Alhoewel daar geen nasionale waaktoesig sisteem vir chirurgiese wondinfeksies is nie, is informasie beskikbaar vir ‘n aantal gevalle wat post-operatiewe wondinfeksie na ‘n keisersnit onwikkel het, maar die noemer en definisie word inkonsekwent gebruik. Die doel van hierdie studie was om die waaktoesig sisteem in Zimbabwe te ontwikkel en te versterk, om ‘n klinies-gebasseerde sisteem te vestig in ‘n opset met beprekte mikrobiologiese toegang, om postoperatiewe chirurgiese wond infeksies na keisersnitte te meet en om die geassosieerde risikofaktore te beskryf en om vas te stel of terugvoering van chirurgiese wondinfeksie data enige effek op die infeksiekoerse na keisersnitverlossings gehad het. Metodologie Hierdie was ‘n voor-en-na studie met twee kohort periodes uitgevoer by twee sentrale hospitale in Harare, Zimbabwe. ‘n Infeksievoorkoming en –beheer intervensie was tussenin uitgevoer. Tydens die pre-intervensie periode was basislyn demografiese en kliniese data ingesamel deur middel van ‘n gestruktureerde vraeboog, en gedurende die post-intervensie fase was die impak van die intervensies gemeet. Gerieflikheidsteekproefneming was geimplementeer. Resultate ‘n Totaal van 290 vroue het toestemming verleen om aan die studie deel te neem in die pre-intervensie periode, waarvan 86.9% (n=252) die 30 day post-operatiewe opvolg voltooi het en die insidensiekoers van chirurgiese wondinfeksies was 29.0% (n=73, 95% CI:23.4-35.0) Intervensies wat onwikkel was het ingesluit: opleiding in Infeksie Voorkoming en -Beheer vir gesondheidswerkers; die implementering van ‘n protokol om chirurgiese instrumente skoon te maak; disseminering van informasie oor post-operatiewe wondhantering vir vroue. Na die implimentering van die intervensie was 314 vroue gewerf in die post-intervensie fase, waarvan 92.3% (n=290) die 30 dae opvolg voltooi het. Daar was ‘n beduidende (p<0.001) verlaging in die insidensiekoers van chirurgiese wondinfeksies na 12.1% (n=35, 95% CI: 8.3-15.8) gedurende hierdie periode. Stellenbosch University https://scholar.sun.ac.za v Daar was bevind dat chirurgiese wondinfeksies beduidend geassosieer was met noodchirurgie (p<0.001), chirurgiese wondklassifikasie IV (p=0.001) en skeer van hare by die huis (p<0.001) by beide die pre-intervensie en post-intervensie periodes. Gevolgtrekking Hierdie studie wys dat keisersnitte uitgevoer kan word met ‘n lae insidensie van chirurgiese wondinfeksies indien toepaslike intervensies, soos opleiding in infeksievoorkoming en beheer, voldoende skoonmaak van toerusting en opvoeding in wondsorg vir die moeders. Dit het ook aangedui dat ‘n eenvoudige data-insameling instrument op ‘n wye basis gebruik kan word in beperkte-hulpbron lande om beleidmakers te help met monitering en evaluering van chirurgiese wondinfeksie koerse, asook die assessering van risikofaktore.